1. Field of the Invention
The present invention relates to novel homogeneous copolyamides based on hexamethylenediamine, adipic acid and fatty acid dimers, and also to certain specific processes for the preparation thereof.
2. Description of the Prior Art
A wide variety of end uses for the various plastics require polymers possessing a particular set of chemical and physical properties, certain of which are characteristic of the polyamides. To the chemical resistance and the tensile strength properties of conventional polyamides, namely, good elongation and good energy absorption, it may be necessary to impart a certain degree of flexibility. A large number of copolymers have been proposed for this purpose, but it is indeed rare to realize all of the desired properties, as the modification required to improve one particular property results in a deterioration in another property.
One advance to the art was made by proposing flexible copolymers based on caprolactam, fatty acid dimers and hexamethylenediamine, which combine, with good flexibility, a tensile strength of more than 5 DaN/mm.sup.2 (deca Newtons per square millimeter) and good resistance to water (compare english patent application No. 2,006,799.
Certain applications may also require copolymers having a better heat resistance and hence, higher melting points. Various experiments had been carried out in accordance with known processes in order to obtain copolyamides based on poly(hexamethylenediamine adipate) and possessing the desired properties, but the homogeneity of the resultant copolymers was always problematical.